The previous wave of buttons for Delicious and Digg and Co.
vanished, Facebook and Twitter and G+ might vanish or they might
survive, but the buttons will vanish for sure. Or do you seriously
think that in ten years we will still have those buttons on every
page? No, right? Why, because you already know as a user that
they’re not that great. So why not get rid of them now? Because
“they’re not doing any harm”? Are you sure?

Update: I don’t think “sleazy” is the right adjective for these buttons. I’d just say they’re distracting, which to me is problem enough.